Abstract

Transition probabilities were evaluated for the and systems of and to analyze the photoexcitation. Franck-Condon factors (FCFs) and Einstein’s coefficients were computed by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of the , , and electronic states and the transition dipole moments for the and systems. The global PESs were determined by the multireference configuration interaction calculations with the Davidson correction and the interpolant moving least squares method combined with the Shepard [Proceedings of the 1968 23rd ACM National Conference (ACM, New York, 1968)] interpolation. The barriers to linearity correcting the spin-orbit interaction are evaluated to be for the state, for the state, and for the state. The obtained FCFs for the and systems indicate that the bending mode is strongly enhanced in the excitation since the equilibrium bond angle greatly varies within the three states. The photoexcitation and fluorescence spectra calculated for the system agree well with the observed spectra. The theoretical lifetimes for lower vibrational levels of the and states were calculated from the fluorescence decay rates for the , , and emissions, and the lifetimes for the state are in good agreement with the observed values except those affected by predissociation.

Received 24 October 2006Accepted 12 December 2006Published online 29 January 2007

Acknowledgments:

The authors are very grateful to Professor H. Ishikawa of Kobe University for providing the experimental data prior to publication and for useful discussions. The computation was partly carried out using SX7 and TX7 owned by the Research Center for Computational Science of The Okazaki National Institutes.